The present invention is directed to optical fiber ribbons containing radiation cured matrix materials and is directed to radiation cured materials suitable for use, inter alia, as matrix materials for optical fiber ribbons. The radiation cured matrix materials have an advantageous combination of physical properties, including good maximum tensile strength and good elongation at high temperatures and provide the optical fiber ribbons with improved heat strippability to allow clean and reliable splicing of the optical fibers.
New optical fiber technologies are continually being developed to accommodate increasing demands for band width and other communication properties. Optical fiber ribbons have been developed to provide increased packing densities, improved accessibility and the like. In the U.S. telecommunications industry, 12-fiber ribbons have become a standard while in Japan, 8-fiber ribbons have commonly been employed. Optical fiber ribbons are disclosed, for example, in the Duecker U.S. Pat. No. 5,881,194, the Lochkovic et al U.S. Pat. No. 5,561,730 and the Hattori et al U.S. Pat. No. 5,524,164, and by McCreary et al, International Wire and Cable Symposium Proceedings (1998):432-439.
Generally, optical fiber ribbons comprise two or more optical fibers embedded and secured within a matrix material. The optical fibers often contain one primary coating, optionally with a secondary coating, or even further additional coatings, and are typically arranged in parallel relation substantially within a single plane to form a ribbon. Ribbon fibers provide a convenient means for splicing fibers as many fibers can be spliced at one time. Generally, to splice the fibers, the matrix material and fiber coatings must be stripped from the fibers which are to be spliced, without damaging the fibers. Thermal stripping tools are conventionally employed to heat the matrix material, for example to a temperature of about 90xc2x0 C. to about 110xc2x0 C., and strip it from a portion of the glass fibers. It is desirable to strip off the coatings in an intact tube form to avoid damage to the optical fibers and/or to avoid deposit of coating debris on the fibers.
Optical fiber ribbon splicing is commonly performed in the field, and, unfortunately, the quality of the stripping operation is operator-dependent owing to variables such as the amount of time the fiber ribbon is heated in the stripping tool and the amount of pressure which the operator exerts on the stripping tool. Accordingly, it is often difficult to obtain a clean strip of the ribbon without disintegration of the coatings and/or the matrix material, and some amount of coating debris typically remains on the optical fibers. Debris on the fibers can interfere with and prevent a clean splice, while attempts to remove such debris can result in fiber breakage. Past attempts to improve the strippability of optical fiber ribbons have focused on primary and/or secondary coating materials typically employed on the optical fibers, as well as strip test parameters, as report by Murata, et al., International Wire and Cable Symposium Proceedings (1997): 281-288, Botelho, International Wire and Cable Symposium Proceedings (1993); 566-569, and Mills, International Wire and Cable Symposium Proceedings (1992): 472-475. These studies among others in the industry generally resulted in improvements in cleanliness upon thermal stripping. However, a need still exists in the fiber optic cable industry for ribbons which reduce the dependence of strippability on such factors.
Accordingly, a need remains for providing improved optical fiber ribbons including a heat strippable matrix material which allows for clean stripping of material from the optical fibers, substantially independent of operator variability.
Accordingly, it is an object of the present invention to provide optical fiber ribbons, and particularly to provide optical fiber ribbons which are heat strippable. It is an additional object of the present invention to provide optical fiber ribbons which overcome disadvantages of the prior art. It is a more specific object of the invention to provide optical fiber ribbons which allow for clean heat stripping of material from the optical fibers and reliable splicing of the stripped fibers. It is a further object of the invention to provide radiation cured matrix materials for use, inter alia, in optical fiber ribbons.
These and additional objects are provided by the optical fiber ribbons and matrix materials of the present invention. More particularly, the invention is directed to optical fiber ribbons which comprise at least two optical fibers encapsulated within a radiation cured matrix material having an advantageous combination of physical properties, including good maximum tensile strength and good elongation at high temperatures. In a more specific embodiment, the matrix materials exhibit a maximum tensile strength at 100xc2x0 C. of at least about 1000 psi and an elongation at break at 100xc2x0 C. of at least about 15%. The present invention is also directed to radiation cured matrix materials, wherein the radiation cured matrix materials exhibit a maximum tensile strength at 100xc2x0 C. of at least about 1000 psi and an elongation at break at 100xc2x0 C. of at least about 15%.
The optical fiber ribbons according to the present invention are advantageous in that the matrix material and any underlying coatings are easily and cleanly heat strippable from the optical fibers in an intact unit and therefore allow for reliable splicing of the stripped fibers in the field, independent of operator variability. The matrix material also exhibits a good combination of mechanical and chemical properties which are otherwise necessary for encapsulating and protecting the optical fibers within the ribbon structure.
These and additional objects and advantages provided by the optical fiber ribbons and matrix materials of the present invention will be more fully apparent in view of the following detailed description.